Chemical mechanical polishing is one technique utilized to process the outer surface of various layers formed over a semiconductor wafer. One principal use of chemical mechanical polishing is to render an outer wafer surface of a layer or layers to be more planar than existed prior to starting the polishing. Only some or all of the outermost layer being polished might be removed during such a process.
In chemical mechanical polishing, both the wafer and the pad which polishes the wafer are typically caused to rotate, typically in opposite directions during the polishing action. A liquid slurry is received intermediate the wafer and the polishing pad. The slurry comprises a liquid solution, typically basic, and a solid abrasive grit material, typically constituting particles of a consistent size (i.e., within 5 nanometers of a typical selected size from around 25 to 100 nanometers in diameter). The action of the liquid solution and abrasive grit within the slurry intermediate the wafer pad and wafer imparts removal of outer wafer layers utilizing both chemical and mechanical actions.
One particular goal in the development of chemical mechanical polishing slurries is the provision of particles of substantially uniform size. As identified above, the typical individual particle size of chemical mechanical polishing slurries is less than about 100 nanometers. Manufactured materials of this fine size are commonly referred to as nanomaterials or nanoparticles. Such materials find use in polishing processes and materials other than chemical mechanical polishing, for example in batteries and in chemical reaction catalysts. Such materials have historically been fabricated using combustion flame synthesis methods, such as for example described in U.S. Pat. No. 5,876,683 to Glumac et al. More recently, laser synthesis of nanoparticles is also gaining interest, such as described in U.S. Pat. No. 5,695,617 to Graiver et al., Laser Synthesis of Nanometric Silica Powders, by M. Luce et al., and Synthesis of Polymerized Preceramic Nanoparticle Powders by Laser Irradiation of Metalorganic Precursors, by P. R. Strutt et al., which are hereby incorporated by reference.
It would be desirable to improve upon the laser synthesis methods, and to produce improved chemical mechanical polishing slurries independent of the method fabrication.